Background: Labor analgesia has been shown to have few undesirable effects on the course and outcome of the labor as well as on the fetal well-being. Aims: This study aims to assess neonatal outcome following lumbar epidural analgesia with intermittent boluses of 0.1% bupivacaine with fentanyl. The secondary objectives included assessment of maternal analgesia, complications, and outcome of labor. Setting and Design: Prospective observational study conducted at a tertiary care teaching institute. Subjects and Methods: Sixty-three patients for labor epidural analgesia were recruited. Epidural catheter was inserted in L4–L5 or L3–L4 interspace. After confirmation of the position of catheter, 3 mL of 0.5% bupivacaine with 20 μg of fentanyl made to 15 mL was administered. After 30 min, efficacy of analgesia was assessed by visual analog scale (VAS). The same bolus dose was repeated after 90 min if the patient complained of pain. A maximum of five top-up doses were allowed. Statistical Test Used: Mean and standard deviation, number and percentage Results: After 30 min of first bolus dose, 93.3% had VAS score of <4. More than 90% patients had adequate analgesia till 4th epidural bolus. During contraction stress test, only two fetuses had late deceleration. About 80% and 98.3% newborns had Apgar of >7 at 1 and 5 min, respectively. Umbilical cord blood pH was ≥7.1 in 98.3% neonates with base excess of >−12. 58.3% delivered normally, 23.3% had instrumental vaginal delivery, and 18.3% required cesarean section. Conclusion: Lumbar epidural analgesia with 0.1% bupivacaine with fentanyl provides optimal neonatal outcome, labor analgesia, and labor outcome.

Keywords: Analgesia, bupivacaine, epidural, fentanyl, labor

How to cite this article:Kesavan R, Rajan S, Kumar L. Effect and safety of labor epidural analgesia with intermittent boluses of 0.1% bupivacaine with fentanyl on fetal and maternal outcomes and wellbeing. Anesth Essays Res 2018;12:769-73

Labor pain is associated with both maternal and fetal adverse effects. In the course of normal labor, these stresses are well tolerated by many healthy parturients with adequate uteroplacental perfusion. However, as a consequence of labor pain maternal and or fetal decompensation can occur especially in the presence of maternal coexisting diseases, uteroplacental insufficiency or when the course of labor becomes complicated. Effective pain relief can alleviate the stress response and improve the outcome in such situations.

The beneficial effects of labor analgesia have been well documented; at the same time, it is also shown to have few undesirable effects on the course and outcome of the labor as well as on the fetal well-being. These include increased incidence of instrumental deliveries, cesarean sections, and depressed neurobehavioral status in the fetus secondary to the effect of anesthetic drugs on the fetus and neonatal asphyxia.[1]

Aim of the study

The primary objective of the study was to assess neonatal outcome following institution of lumbar epidural analgesia with 0.1% bupivacaine with fentanyl during labor. The secondary objectives included assessment of maternal pain relief (quality of analgesia), complications and outcome of labor in terms of normal or assisted vaginal delivery or cesarean section.

Subjects and Methods

This was a prospective observational study conducted in 63 consecutive patients who had undergone labor epidural analgesia with specified protocol after obtaining patient consent and clearance from the Institutional Ethical Committee. Three patients were excluded from the study due to congenital anomalies of the fetus. Those with a history of the previous cesarean section, preeclamptic toxemia of pregnancy, fetuses with congenital malformations, abnormalities in parturients' spine, history of psychiatric illness, neurologic illness, twin pregnancy, and those scheduled for elective cesarean section were excluded from the study.

Those consenting parturients in early labor, as evidenced by cervical dilatation <5 cm and regular uterine contractions, were inducted in our study. On admission, a full medical, obstetric, and anesthetic history was taken. This was followed by a detailed medical and obstetric examination. The preanesthetic evaluation also included assessment of fetus, which included gestational age, fetal presentation, fetal growth, and fetal well-being. Basic investigations such as complete blood count, blood grouping, urine routine, and microscopic examinations were done. All parturients were of the American Society of Anesthesiologists physical status Class 2 and either primipara or second gravida.

All patients were hydrated with 500 mL of normal saline or Ringer's lactate. Baseline maternal blood pressure, heart rate (HR), and fetal HR were recorded. The epidural space was identified by the loss of resistance technique. The epidural catheter was inserted in L4–L5 or L3–L4 interspace and the epidural catheter was threaded 3–4 cm into the epidural space before fixing it.

After confirmation of the position of the catheter, 3 mL of 0.5% bupivacaine with 20 μg of fentanyl made to a total volume of 15 mL was injected slowly through the catheter (15 mL of 0.1% bupivacaine and 20 μg fentanyl). Care was taken not to administer the drug during uterine contractions.

Maternal blood pressure at 10, 20, 30, and 60 min after giving each bolus dose was documented. Automated oscillatory noninvasive blood pressure recording was used to minimize observer bias. Continuous maternal and fetal HR monitoring were done. Verbal communication with the parturient was maintained. After 30 min, the efficacy of analgesia was assessed by visual analog scale (VAS). If there was no pain relief, the catheter was repositioned or reinserted in another space if the patient was willing to do so. The patient was cared for in the lateral position to avoid aortocaval compression.

The intensity of motor blockade was assessed by Bromage scale 30 min after each bolus dose. The same bolus dose was repeated after 1½ h if the patient complained of pain. A maximum of five top-up doses were allowed which would provide analgesia for about 8 h. The outcome of labor was assessed in terms of normal vaginal delivery, assisted vaginal delivery, or cesarean section. Fetal well-being was assessed by Apgar score at 1 and 5 min and by pH and base excess of umbilical cord blood.

The following maternal complications such as maternal hypotension, unintentional dural puncture, unexpected high block, motor blockade, pruritus, and headache were looked for. Maternal hypotension was defined as a systolic blood pressure (SBP) <100 mm of Hg or a fall in SBP >30% of baseline value. Maternal satisfaction was assessed by asking the parturient whether she preferred to undergo labor analgesia in the future pregnancy or encourage her relatives or friends to prefer epidural analgesia during labor.

Continuous variable values were expressed as mean and standard deviation. Categorical variable values were expressed as numbers and percentages.

Results

The mean age of patients was 27.62 ± 2.94 years. Among 60 patients 38 (63.3%) were primigravidae and 22 (36.7%) were multigravidae. Mean cervical dilatation at the time of initiating epidural analgesia was 3.8 ± 1.4 cm.

The mean VAS for assessment of pain before initiating epidural analgesia was 8.05 ± 0.69. After 30 min of giving the first bolus dose, 56 parturients (93.3%) had a VAS score of <4. The mean VAS score was 2.08 ± 1.44, which meant adequate pain relief. Fifty-four patients required second bolus dose of analgesia. The mean VAS score after the second dose of the drug was 2.43 ± 0.83 and 96.3% had a VAS score of <4. Thirty-five parturients were given the third dose of epidural analgesic, the mean VAS score after the third dose was 2.97 ± 0.57 and 91.4% had a VAS of <4. Fourteen parturients were given the fourth bolus of epidural analgesic; the mean VAS after the fourth dose was 3.5 and 92.9% of parturients had a VAS score of <4. Four parturients required fifth epidural bolus of analgesic and the mean VAS score after this was 3.5 ± 0.57 with 50% had a VAS score of <4 and 50% had a VAS of 4 [Figure 1].

Figure 1: Percentage of patients with visual analogue scale more than 4

Out of the 60 fetuses, only two had abnormal HR [Table 1]. Only one had developed bradycardia with a positive contraction stress test. During contraction stress test, only two fetuses had late deceleration of HR [Figure 2].

The 1-min Apgar score was >7 in 39 (80%) neonates and 21 (20%) had an Apgar of <7 and none of them had an Apgar <5. The 5-min APGAR was >7 in 59 (98.3%) neonates, and it was between 5 and 7 in only one [1.7%, [Figure 3]. The umbilical cord blood pH was ≥7.1 in 59 (98.3%) neonates and <7.1 in 1 (1.67%) neonate. The cord blood pH was <7.15 in 3 (5%) of neonates. Fifty-nine neonates had a cord blood base excess >−12 and only one had [Table 2].

Hypotension was not observed in any case [Table 1]. Motor blockade of the Bromage scale 2 was observed in 4 (6.7%) cases. High sensory block manifested as numbness of upper limbs was seen only in one parturient who was of short stature. There was no respiratory compromise [Figure 4]. Of the 60 parturients, 35 (58.3%) delivered normally, 14 (23.3%) had instrumental vaginal delivery, and 11 cases (18.3%) required cesarean section. Fifty-three out of 60 (88.3%) parturients were satisfied with the pain relief obtained by the labor epidural analgesia and expressed their willingness for epidural analgesia during the next pregnancy.

Labor is a painful event and for majority of women, it may be the most painful event that she ever experienced. There are no physiological advantages gained from labor pain. Instead pain of labor often results in excessive maternal suffering, increased mechanical work, marked maternal hyperventilation and increased oxygen demand. The natural response to the pain of labor results in rising catecholamine levels leading to uterine hypoperfusion, fetal hypoxia, and acidosis.

To overcome these maternal and fetal adverse responses to labor pain and also to make childbirth free of pain, various methods have been tried. Among these, the analgesia provided by epidurally administered local anesthetic agents was found to be superior in terms of maternal pain relief and fetal safety. This is evident by the continued increase in the use of this technique over the past 20 years. However, there are concerns regarding the unintended maternal, fetal, and neonatal effects of epidural analgesia. There is sufficient evidence to conclude that epidural analgesia is associated with a lower rate of spontaneous vaginal delivery, a higher rate of instrumental vaginal delivery and prolonged labor.[1] Although in the recent years, neuraxial analgesia has been recommended as the gold standard for obtaining labor analgesia in the absence of specific obstetric contraindications,[2],[3] concerns regarding its safety and maternal outcome still exist among obstetricians. Recent systematic review and meta-analysis have proved that as compared to nonepidural analgesia, epidural analgesia with low concentration of local anesthetic did not result in prolonged duration of the second stage of labor or an increased instrumental delivery rate.[4]

Neuraxial analgesia techniques and medications provide flexible and effective analgesia during labor with minimal motor blockade.[5] Bupivacaine is one of the preferred local anesthetic in labor epidural analgesia because it is highly protein bound (94%) and hence has longer duration of action. At low concentrations, it produces good sensory blockade with minimal or no motor blockade. It has minimal placental transfer, thereby producing low feto/maternal blood ratio at delivery (0.31–0.44). It does not produce tachyphylaxis. The addition of opioids will allow giving a more dilute solution of local anesthetic to provide excellent analgesia during labor.

Advantages of a decreased total dose of local anesthetic include decreased risk of systemic local anesthetic toxicity, decreased risk of high or total spinal anesthesia, decreased plasma concentration of local anesthetic in the fetus and neonate and decreased the intensity of motor block. In our study, only 3.3% had abnormal HR. For one fetus, tachycardia was present even before initiating epidural analgesia. Only one developed bradycardia with a positive contraction stress test. During contraction stress test, only two fetuses had late deceleration of HR which warranted lower segment cesarean section. One of it was due to cord around the neck.

The neonatal depressant effects of drugs administered intrapartum to mother are commonly assessed with neurobehavioral testing, which are very subjective and lack specificity. The addition of fentanyl (2 μg/ml) to bupivacaine 0.125% when used for labor epidural was found to decrease the time of onset of analgesia and increase the duration of analgesia and level of maternal satisfaction during labor as compared to fentanyl (1 μg/ml).[6] Epidural fentanyl up to 2.5 μg/mL administration does not usually result in either accumulation of the drug or subsequent neonatal respiratory depression. The Apgar score rates the five physical signs and is used to assess the condition of the infant at birth, but it is not specific for the effects of anesthesia on the newborn.[7] In our study, the 1 min Apgar score was found to be <7 in 20% of neonates whereas none of them had an Apgar <5, which needed active resuscitation. The 5-min Apgar, which correlates with the long-term neurological outcome, was >7 in 98.3% neonates. The findings of APGAR scores at 5 min was comparable to studies by Anwar[8] and Antonakou.[9]

Cord blood gas analysis is the gold standard for assessing fetal acid-base status and uteroplacental function at birth. Cord blood pH and base excess reflect fetal and immediate neonatal condition. Normal values vary depending on the influence of many factors including duration of labor, parity, etc. They are also affected by sampling techniques. Preanalytical error can be introduced if the cord is not clamped immediately, if air is present in the syringe, or the sample is kept at room temperature for >15 min. The normal umbilical artery pH at term is 7.27 ± 0.07 and base excess is –2.7 ± 2.8 mM/L. Risk of neonatal neurologic morbidity is high only when umbilical arterial pH is below 7.0, 14 or base deficit is above 12 mM/L.[10] Infants with pH <7.0 at birth who are not vigorous are at high risk of adverse neurologic outcome.[11]

Reynolds et al.[12] have shown that umbilical artery pH is influenced by maternal hyperventilation. Therefore, the base excess is considered as a better index of metabolic acidosis after labor. Epidural analgesia is associated with improved neonatal acid-base status which signifies that placental exchange is well maintained in association with maternal sympathetic blockade and adequate analgesia. Although epidural analgesia may cause maternal hypotension, longer second stage of labor, and more instrumental vaginal deliveries, these adverse factors appear to be outweighed by benefits to neonatal acid-base status. Sharma et al.[13] in their study evaluated 358 parturients who underwent labor epidural analgesia and found that the incidence of cord blood pH ≤7.20 in 17% of parturients and pH <7.0 in 0.30% cases. In our study, the umbilical cord blood pH was ≤7.2 in 10% neonates and only in 1.7% cases the pH was <7. Regarding base excess, 98.3% neonates had cord blood base excess >−12 and only 1.7% hadIn our study, none of the parturients developed a high or total spinal anesthesia. The use of multi-orifice epidural catheter and careful assessment of the patient's response to the test dose reduce the chance of unintentional administration of a large dose of local anesthetic into the subarachnoid space. The incidence of hypotension after initiation of neuraxial analgesia during labor was found to be approximately 14%.[14] In our study, only five patients (8.5%) developed hypotension (SBP < 100 mmHg). The lower incidence could be due to preloading with 500 mL of ringer lactate and keeping the parturient in lateral position to avoid aortocaval compression as well as due to the use of a lower concentration of local anesthetic agent.

Pankaj, et al.[15] had reported a dural puncture incidence of 1% in their study. In a meta-analysis of 13 studies by Choi et al.[16] found that the rate of accidental dural puncture with an epidural needle or catheter was 1.5%. The incidence of dural puncture and postdural puncture headache was zero in our study.

In the present study, the incidence of instrumental vaginal delivery was 23.3% and incidence of cesarean section was 18.3%. This slightly higher incidence could be because the decision to perform a cesarean delivery is a subjective one and also due to the inclusion of parturients with precious baby. Whether the labor epidural analgesia increases the incidence of assisted (forceps or vacuum) vaginal delivery and cesarean section is a subject of debate. While systematic reviews of randomized controlled trials comparing neuraxial analgesia with systemic opioids revealed a higher incidence of instrumental vaginal delivery in the neuraxial group, many impact studies have observed no difference in the instrumental vaginal delivery rate before and after the availability of neuraxial analgesia. However, interpretation of these data is difficult due to the presence of multiple confounding factors. Also are indications for instrumental vaginal delivery which is subjective and may vary among obstetricians.[17],[18],[19],[20]

Pruritus and shivering are two common side effects of epidural opioids. Co-administration of local anesthetic decreases the incidence of pruritus. In our study, we found only one case (1.7%) of pruritus. The incidence of shivering is increased by epidural analgesia as the thermoregulatory responses are influenced by multiple factors during labor and delivery including hormonal factors. In our study, the incidence of shivering was only 3.33%, which was comparable to observations made by Desai P et al.[15] The low incidence in our study could be attributed to the use of lower concentrations of local anesthetic agent and addition of opioids.

In our study, 53 out of 60 (88.3%) parturients were satisfied with the pain relief obtained by the labor epidural analgesia and expressed their willingness for epidural analgesia during the next pregnancy. The incidence of failed epidural was 11.7%. The slightly higher incidence of failed epidural in our study may be due to the fact that many of them are performed by trainees with limited experience and because of a smaller sample size.

Conclusion

The institution of lumbar epidural analgesia with intermittent bolus administration of 0.1% bupivacaine with fentanyl can be considered as a safe and effective practice taking into account the optimal neonatal outcome, quality of labor analgesia, labor outcome, and maternal satisfaction.